I have a 1996 polaris sportsman 500 4X4. Will idle great but once it goes past 1/4 throttle it just bogs down.have taken the carb apart like 4 times and didnt find anything out of the ordinary.cleaned it up and same thing.brought it to a guy to have him look at it and went to pick it up it wouldnt start at all had to jump it to get it into my truck.Brought it home got it running and sounded like it was gonna blow up.turns out he didnt put the pilot jet in and it was sitting in the bowl.now its all back together correct and still falls on its face 1/4 throttle. ran the valves 3 times to .006 I think and checked the bumpstick to see if the cam was flat but looked fine.Not sure what else to do and running out of ideas.Anyone have any advice or has the same problem???

 

Choke out of adjustment? I had to take my choke apart not to long ago cause I was running bad. Idles and runs out good now.

 

How did the problem start, all of a sudden one day , after you worked on it, while riding, after it overheated, after filling it up with gas (Bad gas)? Most times, how the problem started, will point you in the right direction.

When you say it runs good under 1/4 throttle, does it move around and have power?

Did you do a compression check?

Could you have any water in the gas? The reason I ask is it sounds like when you go over to the high speed jet, she dies, the high speed jet sits lower in the bowl and will suck water off of the bottom of the bowl. The low speed jet sits higher in the bowl above the water and will alow it to run OK.

 

I bought it on 21 mar 08 and at that time it had a little over 3/4 throttle but pulled pretty strong just some bogging on the high end.did a compresson check and it was 95psi.I have put new air,oil,fuel filts. Drained all the fuel and have premium in it.same thing bogs and pops anything after 1/4 throttle.fuel pump seems to be ok holds pressure and the impulse hose is fine.same thing

 

Well the 95 psi, for your compression test certainlly is low. Not sure if you say this was the psi you have now or this is what is was when you got it in march, but either way it's low. I'd take it again to get a good base line and then add a tablespoon of 30w oil to the cylinder and check it again to see if it comes up.

You didn't mention any excessive oil consumption in your complaint so, I would be suspecting valve problems which could also give you the poping problem along with the slow loss of power over time that you discribe.

You said you reset you valve clearence, were any of the clearences on the tight side, when cold before you adjusted them?

You also could be looking at a weak ignition. How are the plugs looking?

 

I took that reading today 95psi. It never has burned any oil at all. The plug was black but I cleaned it after the last genius looked at it. When I ran the valves they were tight but set em at .006(cold) The ignition looks good to me(nice white hot bolt) What would be the correct psi reading on that motor?

 

Sorry, I don't have specific knowledge for your engine, but I would think you should be up in the 140 psi range to be considered healthy, hopefully someone else with better knowledge than me will jump in here for you.

If your valves were tight when cold, then they were definitely leaking when hot, and could certainly be burnt and leaking now, even after being properly clearenced at this time.

Leaking valves would explain your running discription and power loss. It also, shouldn't be all that easy to start.

 

Believe it or not this thing starts easy and idles like a cadillac.runs perfect till I go past 1/4 throttle.It almost feels like its running out of gas.once I let off the throttle it runs just fine.So you think it could be the valves are bad?

 

Check your clutch. If you've gone through the carb and all looks good check your clutch. The times I've had bogging issues on clutched motors it was the clutch hanging up or just plain wore out rather than carb issues. Pull the cover and belt, check if the clutch is moving freely, visually inspect it for wore sheaves, weights or buttons. Being it's a 13 year old clutch, if stock...there's a good chance it's wore out.

 

<div class="FTQUOTE"><begin quote>Originally posted by: bones202

So you think it could be the valves are bad?</end quote></div>

<u>It's a hard call</u>, but from what you say about low compression, not burning oil, running with tight valve clearences, loss of power over time, it all points in that direction.

I would recommend you have a mechanic diagnos it and then you can deside what to do.

It sounds like you are mechanically inclined and know what you're doing so you might want to tear into it yourself, after you get someone to look at it, that knows that machine.